Util for convert hrefs /PC/NT

I'm copying all my pages to another server (with another name) in test   
purpose. All my links are absolute and I must change every occurrence of   
xxx.company.se to yyy.company.se in 200 files ...

Does someone know a MS-DOS/Windows/Windows NT utility which can replace a   
string in many files (a directory and all sub directories) with another   
string?

Thanks in advance!

Staffan Berger
ElektroPost, Stockholm